Students often use a set block when they want a change block and vice versa. I use the phrase “Set ignores the variable’s old value. Change modifies the variable’s old value.” When students make the mistake of using the wrong block, I’ll ask “do you want to set the variable or change it?” and/or ask them “what’s the difference between set and change?”
Example: "Set ignores the old value. Change modifies the old value."
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